In modern wireless communication systems, it is the task of the receiver to recover with high sensitivity and accuracy baseband signal data or messages which have been transmitted or broadcast by way of modulation on an radio frequency (RF) carrier. With the advent and popularity of mobile hand-held communication systems which operate in the gigahertz region, it is the goal of communication engineers to monolithically integrate the complete high-speed receiver circuit onto a single integrated circuit (IC) chip, the so-called single-chip receiver, so that very light weight handsets can be made available at an affordable price. Indeed, studies of handheld portable and mobile technologies indicate that cost savings by integration alone are in the region of 20-30%. Apart from the direct benefits of size and cost reduction, the benefit associated with the reduction in power consumption, e.g. heat dissipation and battery operation time, is also considerable.
There are however major hurdles which lie on the way to monolithic integration of digital receivers. Firstly, conventional high frequency receivers comprises a large number of discrete components for radio frequency (RF) signal processing. These components often introduce parasitics and other unknowns which are much less repeatable and predictable than circuits made from the IC process. Individual trimming and tuning of such components which are required to make up for the parasitic and other unknown effects further increase costs. On-chip integration of all such components would thus appear to provide an obvious solution. In addition, reduction of off-chip components also minimises the number of power-hungry drivers which are needed to overcome packaging and interconnect parasitics. However, adaptation of current technologies to integrating some of these passive components on-chip is expensive and requires a change of process which requires money and time.
Secondly, monolithic integration of a high speed digital receiver means that high-speed, low-noise small-signal front-end circuitries and high-density, low-power analogue and digital baseband processing circuitries must be put close together. Finding an integrated circuit technology with the right balance of cost and performance is not an easy compromise.